Microclimatic Studies of Urban Open Spaces in Northern Greece

The growth of the cities influences the urban climate and may lead to localized increase of air temperature. Elevated air temperatures, especially during the summer season, may have major implications for building energy demand, local air quality, and outdoor thermal comfort. The present study investigates the thermal behavior of a number of courtyards in the city of Vienna, Austria. Specifically, we explored the diversity of microclimatic conditions in and around a number of geometrically different courtyards. We collected the weather data pertaining to the air temperature, humidity, wind speed and CO 2 , using both mobile and stationary weather stations. Results show the importance of the specific geometry of a courtyard (height-to-width ratio, shading circumstances) in view of the courtyards' microclimate (day-night temperature differences, potential for night-time cooling within the courtyard). When compared to the adjacent street, geometrically open courtyards show slightly more favorable thermal conditions, especially during morning and evening hours.

Sustainable Cities and Society, 2015

In year 2003, United Nations estimated that by year 2030, up to 5 billion people will live in urban areas which will be 61% of the world's population. Urbanization brings major modification on natural landscape; buildings are erected, soil has been transformed into roads and pavement, greenery has been vastly reduced, etc. The deterioration of the urban environment through urbanization can be seen from a phenomenon known as urban heat island (UHI); where cities record higher temperatures in comparison to their non-urbanized surroundings. This study explores the effect of urban texture, characterized by its physical density and form, on the receivable external heat gain, ambient temperature, urban ventilation and outdoor thermal comfort. Addressing these aspects would provide a more comprehensive methodology on urban microclimate analysis, rather being conducted separately. Hence, analysing building performance should be looking not only at a stand-alone (isolated) setting, but also to consider the 'neighbourhood' approach, where urban environment has a significant effect on the energy performance of individual buildings. A series of hypothetical building arrangements are being put into an empty block in a dense urban area, where each of scenarios goes through a series of microclimatic analyses. At the end, this parametric study would narrow down design options which have favourable microclimate condition and acceptable district energy performance.

In Greece, the minimum mandatory distance (D) of a building from the plot's boundaries, relates only to the building's maximum height (H), given as D = 3 + 0.10*H. This is the main institutional tool that shapes urban open spaces and, consequently, the urban microclimate in Greece. In this paper, we will illustrate a numerical model for city planning, named D (b) in an attempt to define mandatory minimum distance between building structures on different plots, taking into account the ground relief and climatic conditions of an area. The methodology we used to create the model is based on bibliographical sources for bioclimatic design. In particular, we were interested in identifying data regarding the sun's height angle (V sun), the height of the building causing shading (Z building), the desired shadow height (Z shadow), and the ground slope (ω). Our model was a pilot one applied in the city planning of a sparsely built area (a separate unit) to be incorporated in the master plan of Serres town in Northern Greece. Two city planning scenarios were developed (one using the presently applied, and the other using the proposed tool), and the results of the expected thermal islet, as given by the two scenarios, were evaluated in comparison. The results of this pilot program suggest that bioclimatic distance between building structures [D (b)] contributes to the utilization of passive energy saving systems. Thus, it could be institutionally utilized and, in combination with currently observed distances, could constitute a valuable addition to the existing city planning tools in Greece.

VITRUVIO - International Journal of Architectural Technology and Sustainability, 2016

Today, the cities need to increase energy efficiency, reduce polluting emissions and achieve a sufficient level of sustainability. The urban microclimate plays an important role on the buildings energy consumption and the feeling of comfort in the spaces. The microclimate parameters are of central importance for the activities that are carried out in the open spaces and to a large extent determine the use. The responses to the microclimate may be unconscious but very often result in a differentiated use of open spaces just as function of the different climatic conditions. For this reason, the aim of this work is focused on the environmental parameters and on the methodology of analysis aiming at the establishment of bioclimatic strategies for buildings on the basis of morpho-type of the components of the geometries and surface quality of the materials used in urban spaces and in function of the consequent microclimatic conditions obtained.

Fresenius Environmental Bulletin (FEB), Volume 16, No 12b-2007, pp. 1619-1626, 2007

Abstract: In Greece, the minimum mandatory distance (D) of a building from the plot’s boundaries, relates only to the building’s maximum height (H), given as D = 3 + 0.10*H. This is the main institutional tool that shapes urban open spaces and, consequently, the urban microclimate in Greece. In this paper, we will illustrate a numerical model for city planning, named D (b) in an attempt to define mandatory minimum distance between building structures on different plots, taking into account the ground relief and climatic conditions of an area. The methodology we used to create the model is based on bibliographical sources for bioclimatic design. In particular, we were interested in identifying data regarding the sun’s height angle (V sun), the height of the building causing shading (Z building), the desired shadow height (Z shadow), and the ground slope (ω).

Journal of Building Materials and Structures, 2018

The present study aims at testing the influence of the urban morphology on the external weather conditions and the urban microclimate by treating quantitative aspects of the outdoor thermal comfort. This is based on a site investigation aims at studying the correlation between the geometry of the street, its orientation and the evolution of the physical variables: air temperature (Ta), Mean Radiant Temperature (MRT), Relative Humidity (RH), Wind speed (Ws). The measures were the subject of a campaign carried out in the urban fabric of the ksar of the red village in the wilaya of Biskra in Algeria. The objective is to define the most efficient urban geometry in term of summer thermal comfort by studying the real impacts of the urban form on the solar control and microclimatic conditions. The evaluation of the thermal comfort in these external spaces is carried out by analyzing physiologically equivalent temperature (PET) values calculated by Rayman Pro 2.1 software based on the measu...

2013

A project on the redevelopment of a large urban area, in the historic centre of Thessaloniki in Greece, has been designed and evaluated based on bioclimatic criteria. The proposed interventions included replacement of pavement materials, addition of trees, fountains, sprinklers as well as external fans and their effects on air and surface temperatures and thermal comfort indices in hot summer conditions have been examined with microclimate simulations. An examination of partial application of the proposed interventions (pavement replacement, trees increase and still water spots) with the latest version of microclimate simulation software ENVImet v3.1betaV has shown mean reduction of 1.5% on ambient temperatures, 16.3% on surface temperatures and 12% on thermal indices at mid summer noon. By integrating water evaporation by fountains and sprinklers in the forthcoming version ENVI-met v4, higher amelioration was observed with ambient and surface temperature reductions of approximately 5% and 17.5% respectively and thermal comfort improvement with PET reduction of 15%. Finally by including the effect of airflow enforcement with external fans, simply as spot wind velocity increase in two squares, pedestrian comfort, calculated with RayMan software was improved by 18% and 41% at noon and up to 35% during the day.

Engineering Research Journal, 2022

With the rapid urbanization and rising affluence, the energy demand and climate change, as well as, health impacts of cities are correlational of increasing importance. Much of this intensive urban growth is wide spreading in parallel with the accelerated climate change detected problems and global warming effects which increasing so broadly as a hot current worldwide stream with facing more of intense and extreme heat waves due to the increase of atmospheric GHG emissions since the industrial revolution. The problem statement is the following: Lack of using climate digital simulation in the conventional urban design process; High dense urban areas are directly influencing the urban heat island effect problems which needs mitigation strategies; Typologies of urban form have a climatic impact on climate orientation inside the districts and also affects the surroundings; Failure of regional climate models to take a consideration of the climatic parameters and human real feeling temperature as on urban microclimate scale and The missing of climate change adaptation strategies in a dynamic design of urban space. The aim of the research will discuss the integrative usage of microclimate digital simulation models to validate the appropriate urban form of an open space in order to be adaptable with climate conditions and to detect the problems of space urban design. Practical urban micro climate scenarios can lead to create a better urban context during different seasons in different climate zones with the consideration of climate parameters through simulating and applying mitigation and adaptation strategies to achieve human thermal comfort in urban outdoor areas and to develop more compatible and healthier urban spaces with enhancing efficient thermal performance using microclimate digital models and find flexible solutions.

Energy and Buildings, 2016

Since some years, dense cities and compact buildings are promoted as sustainable and energy efficient designs. Nevertheless, urban planning strategies should take into account the interactions between buildings and the microclimate because the Urban Heat Island (UHI) phenomenon can increase the cooling load of buildings and is strongly influenced by urban morphology, urban landscaping and the thermal properties of buildings and soil. The modification of these parameters, such as building density, can mitigate UHI, with direct and indirect improvement of building energy performances. The case study presented in this paper concerns a new district in La Rochelle (France) named Atlantech. Currently at the design stage, the goal is to transform this old military camp into a zero carbon district. This study was performed in parallel with urban planning using EnviBatE and SOLENE-Microclimate simulation. Two building densities are compared through the impacts on solar irradiance, wind airflows, building indoor temperatures and energy demand. Analysis of reference and densified district highlights various impacts such as the wind velocity decrease, up to 80%, and the effect on an existing nearby building solar irradiation, reduced by 7%. These results underline the potential usefulness of these simulation tools for urban planners at the design stage.

Climate change and the deriving impacts on the built environment certainly represent one of the most challenging issue for several key players involved in shaping the cities of tomorrow. This is not simply a matter of adapting buildings to new requirements, but rather to rethink the way the urban fabric reacts to new and sometimes unpredictable phenomena. The process is related to increasingly evident extreme conditions in the summer time, that strongly improve the energy demand for cooling with negative impacts on the energy balance as well as on thermal comfort conditions of the end users and of urban population with severe implication on health and wellbeing. Outdoor comfort depends on a number of interrelated factors: the characteristics of the built environment, the relationship between materials and energy use, global climate change and local micro-climate: Temperature, Solar Radiation, Wind distribution, Wind Speed, Absolute and Relative Humidity. The objective of this specific study is to test the microclimate modeling of a city portion in a demo-case – a plot of building blocks with inner courtyards – as a tool for supporting the regeneration phase addressing technological choices and design solutions to improve outdoor comfort conditions. The outcomes of the performed envi-MET simulations, comparing the situation before and after intervention, are consequently discussed. In the specific case, the developed project involving the courtyard has led the Thermal Comfort perception, evaluated in terms of PMV, to shift from " very hot " (+3.50, +4.00 red zone) and " very very hot " (above + 4.50 violet zone) to " Warm " (+1.50, +2.00) at urban plot scale.

The outdoor conditioning is an important research field, especially in the context of sustainable urban development. This paper aims to understand the influence of built environment in microclimatic variations of the open spaces in the city center of Athens, with the intention to identify design strategies for future urban designers which can improve comfort in the outdoor living environment.

Housing Studies, 2012

The quality of life of millions of people living in cities can be improved if the factors that affect the urban microclimate are understood and the form of the city responds to them in a manner that is appropriate to its location. Underlying this approach is the idea that climatically responsive urban design is vital to any notion of sustainability: it enables individual buildings to make better use of 'natural' energy, it enhances the potential for pedestrian comfort and activity in outdoor spaces, and it encourages city dwellers to moderate their dependence on air-conditioned buildings and private vehicles . This paper suggests principles for successful integration of climatic strategies in urban planning processes, and provides case studies illustrating their implementation in practice.

2006

The geometry of an urban area, the choice of the building materials and the surface properties of the dwellings, significantly affect its micro-climate. The city of Athens is mainly composed of narrow streets and large blocks, which raises the already high temperatures, due to the warm macro-climate. The heatwaves of the 1990's increased the annual purchase of air-conditioning systems in Greece by eight times, with most systems having been installed in Athens. This work examines the advantages and disadvantages of open space in Athens, in the form of streets and courtyards, the latter being the uncovered central spaces inside a block of buildings. The investigation is based on urban morphology and air temperature analyses. For the morphology analysis, two different case study sites are considered; the clusters of Amerikis and Omonias. For the air temperature analysis both in-situ temperature measurements as well as the Cluster Thermal Time Constant (CTTC) prediction model are us...

Lighting Research and Technology, 2002

Global and diffuse horizontal illuminance data are analysed for Athens, Greece, for the period 1992-1997. It is shown in a graphical manner that horizontal illuminance (global and diffuse) is dependent upon the time of the day and the month of the year. The diagrams are categorized according to Perraudeau’s nebulosity index, which reflects the sky cover and the climate at a given area. The cumulative frequency distribution of the parameters under all-sky types are estimated and discussed. Some examples of sky-luminance distributions using appropriate software are given. The conclusions are of potential value to local architectural practice, installations of lighting, and in developing an energy-saving policy for the Athens region.

Global and diffuse horizontal illuminance data are analysed for Athens, Greece, for the period 1992-1997. It is shown in a graphical manner that horizontal illuminance (global and diffuse) is dependent upon the time of the day and the month of the year. The diagrams are categorized according to Perraudeau's nebulosity index, which re ects the sky cover and the climate at a given area. The cumulative frequency distribution of the parameters under all-sky types are estimated and discussed. Some examples of sky-luminance distributions using appropriate software are given. The conclusions are of potential value to local architectural practice, installations of lighting, and in developing an energy-saving policy for the Athens region.